You will have to do it by yourself, depending on your skills it can be done with rclone directly from the server, or with something like cyberduck from your computer.
In any case you have to keep original WordPress folder structure year/month/file
Awesome. So as long as the folder structure at the root of the space matches to what WordPress is expecting for a media folder, it should all just work?
Nevermind, I answered my own question. Looks great so far, thanks.
If anyone else is interested, just using Chrome and uploading entire folders via the Digital Ocean Spaces UI is a really easy way of doing this.